three monitors

[bdhaddix]

How do I connect three monitors to an HP ProDesk 400 G4 Desktop Mini PC 4BC39UT

[WAWood]

Probably the reason no one has replied to you so far is that these models are available with a host of different display options and the ones yours support depends entirely on what options were configured on your model.  You could have both onboarc video and a separate video card.  You need to look at the video jacks in the back.  If you have one or two on the case, and one or two more on a card, then you have both types of video, but you can only use one of the two.

So, the answer depends on how many video jacks are available.  I have a video card with 4 HDMI ports and ALL of them can be used at the same time.  But most cards have only three ports and even then, there are often restrictions on what combination of ports can be used.  My previous card had VGA, HDMI, and DisplayPort (DP) but you could not use BOTH the HDMI and DP together.

The best way to find out is by hooking up monitors to see what displays.

If you can only get two monitors to display, then look online for a USB-to-Video adapter.  I used one previously with the three port card so I could use all three monitors at the same time.

Good Luck